Chemical bonds
Covalent Bonds sigma bonds and pi bonds for LCAO-description of such bonding. polar covalent bond is a covalent bond with a significant ionic character. This means that the electrons are closer to one of the atoms than the other, creating an imbalance of charge coordinate covalent bond is one where both bonding electrons are from one of the atoms involved in the bond. These bonds give rise to Lewis acids and bases. The electrons are shared roughly equally between the atoms in contrast to ionic bonding. Such bonding occurs in molecules such as the ammonium ion (NH4+) and are shown by an arrow pointing to the Lewis acid. Also known as non-polar covalent bond Ionic Bonds ;ionic bonds: can be seen as an exanmple of an extremeely polar covalent bond In a simplified view of an ionic bond, the bonding electron is not shared at all, but transferred. In this type of bond, the outer atomic orbital of one atom has a vacancy which allows addition of one or more electrons. These newly added electrons potentially occupy a lower energy-state (effectively closer to more nuclear charge) than they experience in a different atom. http://en.wikipedia.org/wiki/Chemical_bond Pi and Sigma bonds http://en.wikipedia.org/wiki/Pi_bond metallic bonds ;metallic bond. :In this type of bonding, each atom in a metal donates one or more electrons to a "sea" of electrons that reside between many metal atoms. In this sea, each electron is free (by virtue of its wave nature) to be associated with a great many atoms at once. The bond results because the metal atoms become somewhat positively charged due to loss of their electrons, while the electrons remain attracted to many atoms, without being part of any given atom. Metallic bonding may be seen as an extreme example of delocalization of electrons over a large system of covalent bonds, in which every atom participates. double bonds (http://en.wikipedia.org/wiki/Double_bond) ;typical double bond: consists of one sigma bond and one pi bond; for example, the C=C double bond in ethylene. A typical triple bond, for example in acetylene, consists of one sigma bond and two pi bonds in two mutually perpendicular planes containing the bond axis. Two pi bonds are the maximum that can exist between a given pair of atoms. Quadruple bonds are extremely rare and can be formed only between transition metal atoms, and consist of one sigma bond, two pi bonds and one delta bond. A pi bond is weaker than a sigma bond, but the combination of pi and sigma bond is stronger than either bond by itself. The enhanced strength of a multiple bond versus a single (sigma bond) is indicated in many ways, but most obviously by a contraction in bond lengths. For example in organic chemistry, carbon–carbon bond lengths are 154 pm in ethane, 134 pm in ethylene and 120 pm in acetylene. More bonds make the total bond shorter and stronger. triple bonds (http://en.wikipedia.org/wiki/Triple_bond) ;triple bond: in chemistry is a chemical bond between two chemical elements involving six bonding electrons instead of the usual two in a covalent single bond. The most common triple bond, that between two carbon atoms, can be found in alkynes. Other functional groups containing a triple bond are cyanides and isocyanides. Some diatomic molecules, such as dinitrogen and carbon monoxide are also triple bonded. In skeletal formula the triple bond is drawn as three parallel lines (≡) between the two connected atoms; in typography, this is accomplished with the identity operator.12 Triple bonds are stronger than single bonds or double bonds and they are also shorter. The bond order is three.